1. Field of the Invention
The present invention relates to an actuator apparatus for driving a driven member by utilizing an extension/contraction function of a piezoelectric element and/or an electrostrictive element.
2. Description of the Related Art
U.S. Pat. No. 4,894,579, for example, discloses a conventional piezoelectric actuator wherein one end of a piezoelectric element is fixed to a moving member which is put in slidable frictional engagement with a stationary member, and the other end of the piezoelectric element is fixed to an inertia member. When the piezoelectric actuator is operated, the piezoelectric element is extended or contracted quickly so as to accelerate the inertia member. A resultant inertia force is transmitted to the moving member, and thereby the moving member is slid over the stationary member and the piezoelectric actuator runs by itself.
In addition, for example, Jap. Pat. Appln. KOKAI Publications Nos. 4-63309 and 4-69071 disclose structures wherein the above-described actuator is utilized to drive a camera lens. For example, Jap. Pat. Appln. KOKAI Publication No. 4-177214 discloses a structure wherein the above actuator is utilized to drive an optical system of an endoscope, to bend a treatment instrument to be inserted into a body cavity, to open/close a forceps, etc.
However, in the above conventional structures, one end of the piezoelectric element of the piezoelectric actuator is fixed to the moving member and the other end of thereof is fixed to the inertia member. Consequently, the number of structural parts increases, the size of the entire piezoelectric actuator increases, and the processing and assemblage costs increases.
Furthermore, when external mechanical shock is applied to the piezoelectric actuator, the inertia force of the inertia member acts on the piezoelectric element. As a result, a very large load acts on the piezoelectric element, and the piezoelectric element may be destroyed.